Synchronizing apparatus for photo-telegraphy



June 23, 1936. A. G. COOLEY 2,045,294

SYNCHRONIZING APPARATUS FOR PHOTO-TELEGRAPHY Original Filed Dec. 11, 1924 n ln Ill llllll'l lllllllIHllllllllllllI I J I 75' r [m 6.0 45 I r 5 v 49 QIAZ A3 A4 V ENTOR W ATTORNEYJ I v umw 4 Patented June 23, 1936 SYNCHRONIZING APPARATUS FOR rno'ro-rELEGaArnY Austin G. Cooley, New York, N. Y., assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Original application December 11, 1924, Serial No. 755,336, now Patent No. 2,015,742, dated October 1, 1935.

Divided and this application December 22,1931, Serial No. 582,550

8 Claims. (Cl. 178-695) This invention relates to photo-telegraphic apparatus of the type wherein the light values of the subject matter affect the transmitted power so that the light values are reproduced at the receiving station in corresponding time and space relation, and particularly to apparatus for synchronizing the transmitting and receiving units such as, for example, rotating carriers for the photographic or printed matter to be transmitted and received. V

In one aspect the invention comprises apparatus for sending with alternating or other varying current, the transmitter being driven at arate proportional to a power frequency, the subject' matte'r being transmitted by varying the amplitude of the aforesaid current or power; and apparatus for operating the receiver apparatus at a speed proportional to the frequency of said current or power together with means for applying driving forces to the receiver independently of the transmitted power.

In a more specific aspect the invention comprises apparatus for sending with alternating or other pulsating current, the transmitting carrier or transmitter being driven by the source of the current energy or otherwise at a rate proportional to the frequency of the current and the subjectmatter being transmitted by varying the pulsating current, apparatus for driving the receiving carrier or receiver at a speed proportional to said frequency and therefore in synchronism with the transmitting carrier, motive means for applying driving force to the receiver independently of the pulsating transmitting current, and regulating means responsive to the impulses of said pulsating current for synchronizing the receivers with the current frequency and therefore with the transmitter. Said motive means, which may be an electric motor or other motor, preferably applies to the receiving carrier an approximately constant driving force suiilcient to overcome its average resistance,- and said regulating means therefore requires only a small amount of energy to synchronize the carrier. When the regulating means is in the form of a coil inductively associated with the rotor of said motor or with an asassociated rotor it functions as motive means to apply'advancing force when the receiver tends to lag and to apply retarding force when the receiver tends to move too fast, the coil deriving its energy from said pulsating transmitting current or current controlled thereby.

For the purpose of illustration one concrete embodiment of the genus of the invention is shown diagrammatically in the accompanying drawing in which- I Fig. lindicates the transmitting apparatus; and

Fig. 2 indicates the receiving apparatus.

In the particular embodiment of the invention chosen for the purpose of illustration the transmitting apparatus comprises a drum I upon which the photograph, printed matter or the like, is wrapped, a motor 2 for rotating the drum through gears 3 and I, the drum-threading axially on a 10 stationary shaft 5 as it rotates, a generator 6 for, supplying alternating current to variable transformer I at a suitable frequency (say 1000 cycles or higher) which is proportional to the speed of drum l, a photo-electric cell a, a light source a, 15 lenses l0 and II for focusing. upon said cell through apertured plate l2 a pencil of light reflectedfrom the photograph or the like, an audion l3 having its grid l4 and cathode l5 connected to said cell through an input circuit l6 containing a source of potential l1, and having its cathode and anode l 8 connected to an output cir-' cult l9 containing a variable source 20, and an amplifier Al interposed in the output circuit. This amplifier, as well as the amplifiers herein- 25 after referred to, may be of audion or other suitable type. The transformer l is connected across the input circuit It by circuit 2! containing a low capacity (e. g. 0.00001 m. f.) condenser 22, or high resistance 22', (e. g. ofthe order of five to twenty-five megohms, preferably'the latter, depending on the type of audion, etc.)

The receiving apparatus shown in Fig. 2 com prises a drum 23 which rotates without endwise progression, this drum carrying sensitized paper or other suitable recording media. Connected to the drum through gears 24 and 25 is a threaded shaft 26 along which travels a head 21, the head having an opening to receive stationary rod 28 which restrains the head from turning with the shaft. Head 21 carries a needle 29 for directing an electronic discharge to the sheet wound on drum23. This discharge is produced by an oscillatingcircuit 30 feeding into circuit 3| containing coil 32 and condenser 33, the oscillating circuit being controlled by the aforesaid transmitting station working through amplifiers A2 and A i a modulator 34. g

The oscillator comprises a circuit 35 connv ct to the grid 36 and anode 3i of audion 38 and containing battery 39, condenser 40 and coil 4|, the latter being inductively associated with coil 32. The output circuit 42 from the cathode 43 and anode 44 of modulator 341s connected between the coil ii and cathode 45 of audion 38, the grid 46 of the modulator being connected to amplifier Al, through transformer 41. A condenser is may be connected in the circuits by switch 4! but is ordinarily not required.

Gearedtothedrum Ilisashaftllcarryinga conducting disk 4! and geared to shaft ll is a shaft ll waving a conical rotor II of paramagnetic material, the rotor having peripheral poles I2 and an axial stem 53 fast to shaft III. Stationary coils l4 and 55 are associated with the poles l2 and stem 53 respectively, 'the coil 55 being energized by battery 58 to polarize poles i2 and also to pull upwardly on stem 53 thereby to cause the shaft I. to rest lightly on bearing 51. The coils N are connected to amplifier A3 through circuit 58 containing switch 59. Associated with disk 49 are electro-magnets 60 connected to a variable source of alternating current II through circuit II containing condenser 63 to throw magnets I out of phase with each other and switch I. The circuit 58 may also be connected to electro-magnets associated with disk I! and in the drawing this circuit is connected to electro-magnets 65 other than magnets I through circuit I containing switch 01, a condenser 15 being connected in series with one of the electro-magnets 85 to produce the necessary phase displacement.

In transmitting, motor 2 drives the drum I at a speed p p rtional to the frequency of the alternating current from generator 8 and the light from source traces a spiral around the periphery of the drum as the latter is threaded along shaft from the subject-matter on drum I to the photoelectric cell varies the resistance of circuit II in accordance with variations in the reflection ability of the successive points of the subject-matter. This variation of resistance in circuit I! vsrice the potential on grid I4 and thereby varies the aforesaid impulses.

It has been found that by varying the potential of battery 2| either like or opposite reproduction can be effected, that is, either a positive or a negative can be produced at the receiving station when using a negative (or a positive) at the transmitting station. For example, like reproduction has been attained with twenty volts and opposite reproduction with ten volts. This is due to the fact that under the respective conditions opposite effects are produced by the pulsating potential impressed upon grid I I by transformer I when the plate potential is varied. A theory explanatory of this mode of operation is set forth in copending application Serial No. 755,337, filed Dec. 11, 1924, now Patent No. 1,593,651, granted July 27, 1926, in which application this method of like or opposite reproduction is claimed.

At the receiving station said varying impulses vary the potential on grid 45 thereby varying the effective resistance of circuit 42 and varying the intensity of the oscillations in circuit 30. When no impulse is acting upon grid 46 the resistance of the modulator is sufficient to prevent oscillations or at least render the oscillations so feeble as to be ineffective. When an impulse is acting upon grid 46 the resistance is lowered sumciently to permit oscillations, the intensity of the oscillations being proportional to the intensity of the impulse. Theoscillating circuit 30 is preferably adjusted to generate oscillations of high-frequency and high-potential adapted to produce an electronic discharge (e. g. a corona discharge) from needle as when above a predetermined intensity higher than that existing between successive impulses, the intensity of the discharge 5 depending upon the excess of oscillation intensity above the predetermined intensity, whereby an electronic discharge is emitted from needle is during each impulse (except perhaps while recording a white or an extremely light representation on the receiving paper.) Thus, in transmitting a half-tone. a dot (or short dash) is recorded on the receiving paper at each impulse, the dot varying in intensity in response to variations in the intensity of said impulses, and in transmitting extreme contrasts such as the black and white of printed matter, at each impulse during passage of black or white (depending upon the adjustment of the transmitting apparatus as above described) past the point of incidence of the light from source 9.

The recording paper may be of the type requiring development subsequent to exposure by the electronic discharge to convert the latent image into a patent image or it may be of the type in which a patent image is produced without development, the latter type having the advantage of displaying the image as it is recorded. The electronic discharge produces the exposure as a result of its light and/or heat and/or electronic bombardment of the photographic emulsion.

The receiving drum 23 is driven at approximately the speed of the transmitting drum I by the eddy-current motor comprising disk 49, the

current in coils ill being adjusted to such quantity and phase relation as to overcome the average resistance of the parts driven thereby, and the aforesaid impulses of current synchronize the drum 28 with drum I by recurrently energizing magnets 54 at the frequency of the transmitting current. The poles I! are so distributed that one pole passes each magnet l4 during each impulse. Ifthemotorflisdrivingthedmmflatsynchronous speed the alternate advancing and retarding effects of the magnets 54 cancel, whereas if motor It tends to drive drum 23 too slow ortoo fast either the advancing or the retarding effect of magnets I4 predominates to maintain the drum in synchronism.

By closing switch I! power is supplied to motor 40 in proportion to the intensity of the transmitting impulses, and the power of the eddy-current motor is thereby varied in accordance with the current synchronous motor II-Sl, thus more effectively holding the drum in synchronism dining modulating the synchronizing pulsations it will be understood that in its broader aspect the present invention is independent of whether or not the subject-matter is transmitted by modulating these pulsations or other pulsations. For example,

a second generator I may be connected with the plate circuit I9 through transformer I for producing synchronizing pulsations of diiferent frequency, in which case the receiving apparatus is adjusted to respond to these pulsations and the pulsations produced by generator 6 have no effect upon the synchronizing apparatus owing to their different frequency. It will also be understood that this invention is applicable to multiplex systems wherein a plurality of images or signals are sent simultaneously by modulating osages diiierent pulsations of different frequencies and/or beat frequencies according to the diflerent subject-matter respectively.

This application is a division of application Serial No. 755,336, illed December 11, 1924, now

Patent No. 2,015,742, granted Oct. 1', 1935; and also of application BerialNo. 521,665, ilied March What is claimed is:

1. 'ihe method of synchronizing picture transmission apparatui which comprises driving the transmitting apparatus at a speed determined by the trequency oi the carrier current, and controlling the speed or the receiving apparatus by the modulated carrier current. r

2. Means ior receiving an image represented 3- by a modulated carrier current including a motor, andmeans for applying said modulated carrier current to control the speed 0! said motor.

3. The method of synchronizing apparatus at two places between which transmission is ef-- iected by modulated carrier current, which. consists in determining the speed oi; the apparatus at both places in accordance with thecarrier frequency. j

- 4.. The method of synchronizingth'e transmitting and receiving apparatus in a modulated carrier current communication system, which consists in determining the speed oif both the transmitting and receiving apparatus in accordance with the frequency of the carrier current.

5. In the transmission of pictures by means .ot a modulated carrier current, the method or synchronizing the transmitting and receiving ap- 5 paratus which consists in driving the transmitting apparatus at a speed determined bythe speed oi-the carrier current generator and at the cation to the motor of energy controlled by a 20 continuous series of high-frequency photoelectric. impulses ot-variable' intensity and equal duration. I

- 8. me method of controlling; the speed of a motor such as used in radiographic apparatus-2e which consists .in applying to the motor energy controlled by impulses of equal-duration and oi variable intensity. accom. I 

